This invention relates to a field emission cathode, and more particularly to a field emission cathode which is conveniently used as an electron source for various kinds of equipments such as a display device, a light source, an amplification element, a high-speed switching element, a sensor and the like.
A field emission cathode is greatly increased in electric current emitted therefrom when strength of an electric field applied to an emitter from an exterior thereof is increased. For this purpose, a number of field emission cathodes each including an emitter having tips sharply pointed were proposed. Such conventional field emission cathodes each are typically constructed, for example, in such a manner as shown in FIGS. 11A and 11B. More particularly, the conventional field emission cathode is so constructed that a gate 100 and an emitter 102 having tips 101 formed into a sawtooth-like shape are arranged on an insulating substrate 103 with a groove 104 being interposed therebetween.
Unfortunately, the conventional field emission cathode constructed as described above has a disadvantage in that it is highly difficult to form the tips 101 of the emitter 102 into a uniform sharp shape with good reproducibility. This causes distances between the tips 101 of the emitter 102 and the gate 100 to be non-uniform, resulting in characteristics of the emitter 102 being substantially varied, leading to deterioration in serviceability of the field emission cathode.
In view of the foregoing, the inventors proposed a field emission cathode constructed as shown in FIGS. 10A and 10B. More specifically, in the field emission cathode proposed, an emitter 110 is constituted by a base section 111 and a plurality of tip sections 112 formed into a rectangular shape so as to project from the base section 111. The tip sections 112 are arranged so as to be in close proximity to a gate 113 at microdistances as small as submicrons, to thereby substantially eliminate a variation of characteristics of the emitter 110 and permit the tip sections 112 to be uniformly formed with good reproducibility.
Nevertheless, the field emission cathode proposed causes a voltage which is to be applied to the gate 113 or an operation voltage to be increased as compared with the field emission cathode shown in FIGS. 11A and 11B. Also, it has another disadvantage that the tip sections 112 are damaged or injured due to electrostatic attraction acting between the rectangular tip sections 112 of the emitter 110 and the gate 113.
In the conventional field emission cathode shown in FIGS. 10A and 10B, a relationship of a width of each of the rectangular tip sections 112 to an interval between each adjacent two of the tips 112 is not specifically defined and is set to be approximately 1:1.